The present invention relates to high power output, medium speed diesel engines. More particularly, the present invention relates to a method of lowering fuel consumption and nitrogen oxide emissions in two-stroke diesel engines.
High power output, medium speed, two-stroke diesel engines are used in various transportation applications, such as locomotives and marine engines. Among the problems associated with such engines is the level of nitrogen oxide emissions (hereinafter referred to as xe2x80x9cNOxxe2x80x9d) in two-stroke diesel engines. As NOx emission standards become more stringent, diesel engines of this type must be modified or manufactured to further reduce such emissions.
For existing two-stroke diesel engine designs, particularly for those engines that are currently in use, one approach to meeting emissions requirements is to retard the start of fuel injection. However, fuel timing retard, which is usually performed during engine rebuild, compromises engine performance by reducing fuel efficiency.
Therefore what is needed is a method of reducing NOx emissions for a two-stroke diesel engine while maintaining the fuel efficiency of the engine. This is of particular importance at rated (or full) speed and load.
A method of lowering fuel consumption and NOx levels in a two-stroke diesel engine having at least one piston disposed in at least one combustion chamber comprises the steps of providing a compression ratio within the combustion chamber between about 16:1 to about 19:1, providing a ratio of peak pressure to compressed pressure within the combustion chamber below about 1.4; and providing a trapped air charge density within the combustion chamber of at least 2.77 kg/m3. Combustion within the diesel engine results in NOx levels in exhaust gases below a predetermined amount and fuel consumption below a predetermined amount.